`type range::RangeOfBounds<T> = (Bound<T>, Bound<T>)`

Proposal

Problem statement

Our range type zoo currently does not cover some cases such as an exclusive-inclusive range or or a type that can flexibly express all cases. In some places the (Bound<T>, Bound<T>) tuple is used as the most type, for general example by the RangeBounds and IntoBounds.

Motivating examples or use cases

For example in https://github.com/rust-lang/rust/pull/162110 it was proposed to add the language

Use (Bound<T>, Bound<T>) if you need a type that can store an arbitrary range.

to Range documentation. It would be better if we could instead point to the std::range module and let users choose an appropriate type. But that requires having the most-general type on that page too.

Solution sketch

Add a type-alias to the range module that exists as a home for documentation and less cumbersome naming for general ranges.

mod range {
   /// Dedicated documentation...
   type RangeOfBounds<T> = (Bound<T>, Bound<T>);
}

The rustdoc page would also show a more-relevant subset of implementations that currently live on the tuple-primitive page

For now I'm not proposing to add any methods to this type alias since those could conflict with more general tuple methods, but with inherent trait impls we could make RangeBounds inherent so users can call contains and is_empty without importing it.

Alternatives

• do nothing
• don't add the alias but mention it in module-level documentation and link to the tuple page
• introduce a dedicated type and migrate to it

Links and related work

Start by reading the std::range documentation and the existing RangeBounds and IntoBounds APIs, then compare the tuple-primitive documentation linked in the proposal. Determine whether a documented RangeOfBounds alias is preferable to module-level links or a dedicated type, and seek library-team agreement before implementation.